Clinical translation of engineered tissue constructs requires noninvasive methods to assess construct health and viability after implantation in patients. However, current practices to monitor post-implantation construct integration are either qualitative (visual assessment) or destructive (tissue histology). As label-free fluorescence lifetime sensing can noninvasively characterize pre-implantation construct viability, we employed a handheld fluorescence lifetime spectroscopy probe to quantitatively and noninvasively assess tissue constructs that were implanted in a murine model. We designed the system to be suitable for intravital measurements: portability, localization with precise maneuverability, and rapid data acquisition. Our model tissue constructs were manufactured from primary human cells to simulate patient variability and were stressed to create a range of health states. Secreted amounts of three cytokines that relate to cellular viability were measured in vitro to assess pre-implantation construct health. In vivo optical sensing assessed tissue integration of constructs at one-week and three-weeks post-implantation. At one-week post-implantation, optical parameters correlated with in vitro pre-implantation secretion levels of all three cytokines (p < 0.05). This relationship was no longer seen at three-weeks post-implantation, suggesting comparable tissue integration independent of preimplantation health. Histology confirmed re-epithelialization of these constructs independent of pre-implantation health state, supporting the lack of a correlation. These results suggest that clinical optical diagnostic tools based on label-free fluorescence lifetime sensing of endogenous tissue fluorophores could noninvasively monitor post-implantation integration of engineered tissues.
Sakib F. Elahi, Seung Y. Lee, William R. Lloyd, Leng-Chun Chen, Shiuhyang Kuo, Ying Zhou, Hyungjin M. Kim, Robert Kennedy, Cynthia Marcelo, Stephen E. Feinberg, and Mary-Ann Mycek, "Assessment of post-implantation integration of engineered tissues using fluorescence lifetime spectroscopy," Proc. SPIE 10484, Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XVI, 104840G (Presented at SPIE BiOS: January 29, 2018; Published: 12 February 2018); https://doi.org/10.1117/12.2290280.
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